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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package text
// parseNumberValue parses a number from the input and returns a Token object.
func (d *Decoder) parseNumberValue() (Token, bool) {
in := d.in
num := parseNumber(in)
if num.size == 0 {
return Token{}, false
}
numAttrs := num.kind
if num.neg {
numAttrs |= isNegative
}
strSize := num.size
last := num.size - 1
if num.kind == numFloat && (d.in[last] == 'f' || d.in[last] == 'F') {
strSize = last
}
tok := Token{
kind: Scalar,
attrs: numberValue,
pos: len(d.orig) - len(d.in),
raw: d.in[:num.size],
str: string(d.in[:strSize]),
numAttrs: numAttrs,
}
d.consume(num.size)
return tok, true
}
const (
numDec uint8 = (1 << iota) / 2
numHex
numOct
numFloat
)
// number is the result of parsing out a valid number from parseNumber. It
// contains data for doing float or integer conversion via the strconv package
// in conjunction with the input bytes.
type number struct {
kind uint8
neg bool
size int
}
// parseNumber constructs a number object from given input. It allows for the
// following patterns:
// integer: ^-?([1-9][0-9]*|0[xX][0-9a-fA-F]+|0[0-7]*)
// float: ^-?((0|[1-9][0-9]*)?([.][0-9]*)?([eE][+-]?[0-9]+)?[fF]?)
// It also returns the number of parsed bytes for the given number, 0 if it is
// not a number.
func parseNumber(input []byte) number {
kind := numDec
var size int
var neg bool
s := input
if len(s) == 0 {
return number{}
}
// Optional -
if s[0] == '-' {
neg = true
s = s[1:]
size++
if len(s) == 0 {
return number{}
}
}
// C++ allows for whitespace and comments in between the negative sign and
// the rest of the number. This logic currently does not but is consistent
// with v1.
switch {
case s[0] == '0':
if len(s) > 1 {
switch {
case s[1] == 'x' || s[1] == 'X':
// Parse as hex number.
kind = numHex
n := 2
s = s[2:]
for len(s) > 0 && (('0' <= s[0] && s[0] <= '9') ||
('a' <= s[0] && s[0] <= 'f') ||
('A' <= s[0] && s[0] <= 'F')) {
s = s[1:]
n++
}
if n == 2 {
return number{}
}
size += n
case '0' <= s[1] && s[1] <= '7':
// Parse as octal number.
kind = numOct
n := 2
s = s[2:]
for len(s) > 0 && '0' <= s[0] && s[0] <= '7' {
s = s[1:]
n++
}
size += n
}
if kind&(numHex|numOct) > 0 {
if len(s) > 0 && !isDelim(s[0]) {
return number{}
}
return number{kind: kind, neg: neg, size: size}
}
}
s = s[1:]
size++
case '1' <= s[0] && s[0] <= '9':
n := 1
s = s[1:]
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
n++
}
size += n
case s[0] == '.':
// Set kind to numFloat to signify the intent to parse as float. And
// that it needs to have other digits after '.'.
kind = numFloat
default:
return number{}
}
// . followed by 0 or more digits.
if len(s) > 0 && s[0] == '.' {
n := 1
s = s[1:]
// If decimal point was before any digits, it should be followed by
// other digits.
if len(s) == 0 && kind == numFloat {
return number{}
}
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
n++
}
size += n
kind = numFloat
}
// e or E followed by an optional - or + and 1 or more digits.
if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') {
kind = numFloat
s = s[1:]
n := 1
if s[0] == '+' || s[0] == '-' {
s = s[1:]
n++
if len(s) == 0 {
return number{}
}
}
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
n++
}
size += n
}
// Optional suffix f or F for floats.
if len(s) > 0 && (s[0] == 'f' || s[0] == 'F') {
kind = numFloat
s = s[1:]
size++
}
// Check that next byte is a delimiter or it is at the end.
if len(s) > 0 && !isDelim(s[0]) {
return number{}
}
return number{kind: kind, neg: neg, size: size}
}
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